This invention relates generally to gas turbine engines, and more specifically to a method and apparatus for controlling fluid leakage through a gas turbine engine.
Gas turbine engines typically include a compressor for compressing air. The compressed air is mixed with a fuel and channeled to a combustor, wherein the fuel/air mixture is ignited within a combustion chamber to generate hot combustion gases. The combustion gasses are channeled to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
Within at least some known gas turbine engines, fluid leakage through seals positioned within the engine may significantly increase fuel consumption, reduce engine efficiency, and, because of a resulting increase in turbine inlet temperature, may also increase maintenance costs for the engine. As is well known, high pressure gases, such as combustion gases within the turbine and compressor discharge air, may leak from higher pressure areas to areas of lower pressure. To facilitate controlling such leakage, at least some known gas turbine engines include labyrinth seals, and/or brush seals positioned between adjacent areas of high and low pressure. However, over time, continued exposure to high pressure and thermal cycling may cause labyrinth seals and brush seals to wear and lose their sealing effectiveness. As a result, labyrinth seals and brush seals may need to be periodically replaced, but to do so, requires the engine to be shut down.
To facilitate extending an amount of time elapsed between engine outages, at least some other known gas turbine engines include gas bearing type seals to facilitate controlling leakage of fluid between areas of generally high and low pressures. However, although such seals do not generally require replacement as frequently as labyrinth and brush seals, known gas bearing type seals are generally much more complex, and therefore their installation and manufacture may be much more time consuming, and expensive. Furthermore, overtime, although such seals generally tend to withstand wear better than labyrinth and brush seals, at least some know gas bearing type seals may vibrate undesirably during operation of the gas turbine engine.